Superconducting materials and devices produced from superconducting materials are known in the art. A characteristic property of a superconductor is its superconductivity, i.e. the disappearance of its electrical resistance when it is cooled below a critical temperature. However, upon the application of a magnetic field equal to or greater than a critical field (Hc2), the superconductivity is lost. Associated with the critical magnetic field is a critical current, i.e. the current at which the superconducting material loses its superconducting properties and reverts back to its normal, i.e. non-superconducting, state. For applied magnetic fields with amplitudes below the critical field, the superconducting state is not lost, but the value of the critical current is reduced. Therefore, the critical current of a superconducting conductor is dependent upon the amplitude and direction of the externally applied field.
In traditional coil, solenoid or toroid designs, one turn—typically the innermost in coils or toroids and the outermost in solenoids—is exposed to a higher magnetic field than the other turns, hence decreasing its critical current and therefore the overall critical current of the superconducting device. Conventional designs do not address this problem. Rather, the limitation of the overall critical current, for example by the current in the innermost turn of a coil, is merely seen as a characteristic of the superconducting device.